A RS of Post-extractional Alveolar Hard and Soft Tissue Dimensional Changes

8/9/2019 A RS of Post-extractional Alveolar Hard and Soft Tissue Dimensional Changes

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Wah Lay TanTerry L. T. WongMay C. M. WongNiklaus P. Lang

A systematic review of post-extrac-tional alveolar hard and soft tissuedimensional changes in humans

Authors’ affiliations:Wah Lay Tan, Terry L. T. Wong, May C. M. Wong,Niklaus P. Lang, Implant Dentistry, The Universityof Hong Kong, Prince Philip Dental Hospital,Implant Dentistry, Hong Kong, China

Corresponding author:Prof. Niklaus P. Lang, DMD, MS, PhD, Dr odont.h.c. mult.The University of Hong Kong Faculty of DentistryPrince Philip Dental Hospital

34 Hospital Road, Sai Ying PunHong Kong, ChinaTel.:+852 2859 0526Fax: +852 2858 6114e-mail: [email protected]

Conflicts of interestThe authors declare no conflict of interest.

Key words: alveolar bone, dimensional change, extraction, hard tissue, human, removal of

teeth, resorption, soft tissue, systematic review

Abstract

Background: Removal of teeth results in both horizontal and vertical changes of hard and soft

tissue dimensions. The magnitude of these changes is important for decision-making and

comprehensive treatment planning, with provisions for possible solutions to expected

complications during prosthetic rehabilitation.

Objectives: To review all English dental literature to assess the magnitude of dimensional changesof both the hard and soft tissues of the alveolar ridge up to 12 months following tooth extraction

in humans.

Methods: An electronic MEDLINE and CENTRAL search complemented by manual searching was

conducted to identify randomized controlled clinical trials and prospective cohort studies on hard

and soft tissue dimensional changes after tooth extraction. Only studies reporting on undisturbed

post-extraction dimensional changes relative to a fixed reference point over a clearly stated time

period were included. Assessment of the identified studies and data extraction was performed

independently by two reviewers. Data collected were reported by descriptive methods. Weighted

means and percentages of the dimensional changes over time were calculated where appropriate.

Results: The search provided 3954 titles and 238 abstracts. Full text analysis was performed for 104

articles resulting in 20 studies that met the inclusion criteria. In human hard tissue, horizontal

dimensional reduction (3.79 ± 0.23 mm) was more than vertical reduction (1.24 ± 0.11 mm on

buccal, 0.84 ±

0.62 mm on mesial and 0.80 ±

0.71 mm on distal sites) at 6 months. Percentagevertical dimensional change was 11 – 22% at 6 months. Percentage horizontal dimensional change

was 32% at 3 months, and 29 – 63% at 6 – 7 months. Soft tissue changes demonstrated 0.4 – 0.5 mm

gain of thickness at 6 months on the buccal and lingual aspects. Horizontal dimensional changes of

hard and soft tissue (loss of 0.1 – 6.1 mm) was more substantial than vertical change (loss 0.9 mm to

gain 0.4 mm) during observation periods of up to 12 months, when study casts were utilized as a

means of documenting the changes.

Conclusions: Human re-entry studies showed horizontal bone loss of 29 – 63% and vertical bone

loss of 11 – 22% after 6 months following tooth extraction. These studies demonstrated rapid

reductions in the first 3 – 6 months that was followed by gradual reductions in dimensions

thereafter.

The periodontium is an important structurethat supports the tooth and is affected by any

changes that the tooth may undergo, includ-

ing eruption and extraction (Cohn 1966; Pie-

trokovski & Massler 1967, 1971). The

alveolar process is a tooth-dependent tissue;

the shape and volume of the alveolar process

is influenced by tooth form, as well as the

direction of eruption of the tooth (Marks

1995; Marks & Schroeder 1996), and the pres-

ence or absence of teeth (Tallgren 1972). Sim-

ilarly, gingival tissues undergo changes

together with eruption and eventual exfolia-

tion or extraction of the tooth. Subsequent toremoval of a tooth, the periodontium under-

goes atrophy (Cohn 1966; Schropp et al.

2003), with the complete loss of attachment

apparatus including cementum, periodontal

ligament fibres and bundle bone (Araujo &

Lindhe 2005).

Tooth extraction is one of the most widely

performed dental procedures. In general, post-

extraction healing of both the hard and soft

tissues proceeds uneventfully. However, the

removal of a tooth will generally result in

some alveolar bone loss, as well as structural

Date:Accepted 15 October 2011

To cite this article:Tan WL, Wong TLT, Wong MCM, Lang NP. A systematicreview of post-extractional alveolar hard and soft tissuedimensional changes in humans.Clin. Oral. Impl. Res. 23(Suppl. 5), 2012, 1–21doi: 10.1111/j.1600-0501.2011.02375.x

© 2011 John Wiley & Sons A/S 1


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and compositional changes in the overlying

soft tissue (Schropp et al. 2003). Both hori-

zontal and vertical changes in dimensions are

expected in hard tissue (Van der Weijden

et al. 2009) as well as soft tissue. Studies in

the canine model (Araujo & Lindhe 2005;

Araujo et al. 2005) have demonstrated that

there are marked dimensional changes of the

alveolar ridge in the first 2 – 3 months post-

extraction, with the changes more pro-

nounced on the buccal (Araujo et al. 2005).

Critically, horizontal buccal bone resorption

has been shown reach as much as 56% while

lingual bone resorption has been reported to

be up to 30% (Botticelli et al. 2004); the over-

all reduction in width of the horizontal ridge

has been reported to reach 50% (Schropp

et al. 2003).

A narrower and shorter ridge can be an

expected sequelae of the resorptive process

(Pinho et al. 2006), and in effect, the process

of resorption often results in the relocation of

the ridge to a more lingual position (Botticelli

et al. 2004). The process of ridge remodelling

is further complicated if the buccal bone wall

is lost (Iasella et al. 2003) as a result of

inflammatory processes or the extraction

itself.

Extraction of one or more teeth results

not only in changes of the bony architec-

ture, but also affects the overlying soft tis-

sues of the alveolus (Schropp et al. 2003).

Immediately following tooth extraction,

there is absence of soft tissue covering over

the socket entrance, and hence the socket

defect is left to heal by secondary intention.

In the subsequent weeks, cell proliferation

will result in an increase in soft tissue vol-

ume, and a soft tissue covering will seal the

socket entrance. The changes in the muco-

sal contours are dependent on the corre-

sponding changes in the external profile of

the alveolar bone surrounding the extraction

site.

The magnitude of these dimensional

changes are important for informed decision-

making and comprehensive treatment plan-

ning, with provisions for possible solutions

to expected complications during prosthetic

rehabilitation. In addition, with the advent of

greater emphasis on aesthetics in the last

decade, a thorough understanding of the

resorptive pattern and alterations in bony and

mucosal contours post-extraction would

greatly enhance our ability to reconstruct our

patients to a level of optimal function cou-

pled with satisfactory aesthetics.

There have been numerous studies that

have researched the magnitude of hard tissue

changes post-extraction, with the consensus

that alveolar bone loss can be quite marked

after tooth removal (Araujo & Lindhe 2009),

especially in the horizontal dimension (Botti-

celli et al. 2004). Soft tissue changes

post-extraction have largely been described

qualitatively, and usually as a single entity

together with the hard tissue changes

assessed using serial study casts (e.g. Schropp

et al. 2003).

In recent years, there has been one system-

atic review addressing the dimensional

changes of the alveolar ridge after tooth

extraction (Van der Weijden et al. 2009);

however, there is as yet no systematic review

addressing the dimensional changes of both

the hard and soft tissues after tooth extrac-

tion.

This study aims to review all existing liter-

ature published between 1st January 1960

and 30th January 2011, to assess the magni-

tude of dimensional change of both the hard

and soft tissues of the alveolar ridge after

tooth extraction.

Material and methods

The Preferred Reporting Items for Systematic

Reviews and Meta-Analyses (PRISMA) state-

ment was consulted throughout the process

of this systematic review.

Focused question

What is the magnitude of dimensional

changes in the hard and soft tissues of the

alveolar process, up to 12 months following

tooth extraction?

Search strategy

A comprehensive and systematic electronic

search of both the MEDLINE – Pubmed data-

base and the Cochrane Central Register of

Controlled Trials (CENTRAL) was con-

ducted, for articles published in English

between 1st January 1960 and 30th June

2010 in the dental literature. The search

was performed again at a later stage, to

include any relevant new studies published

between 1st July 2010 and 31st Janu-

ary 2011. The following key words were

used:

Intervention:

(

OR

OR

)

AND

Outcome:

(

OR)

The following journals between 2004 and

2010 inclusive, were hand-searched for rele-

vant articles: Clinical Oral Implants

Research, International Journal of Oral &

Maxillofacial Implants, Implant Dentistry

Journal of Periodontology, Journal of Clinical

Periodontology and Journal of Oral Implan

tology .

Furthermore, the bibliographies of all pub-

lications selected for inclusion in this review

were also scanned for potentially relevant

articles.

Selection criteria

Studies were included if they were published

in English and conducted on human subjects,with the intervention being tooth extraction,

and the outcome to be assessed in the form

of changes in the clinical or radiographic

alveolar bone dimensions, as well as dimen-

sional soft tissue changes. Similarly, exclu-

sion criteria were applied; letters and

narrative or retrospective reviews, single case

reports, case series with less than three cases,

and third molar extraction cases were all

excluded. Only studies reporting on undis-

turbed post-extraction dimensional changes

relative to a fixed reference point over a

clearly stated time period were included. Inaddition, in the event of duplicate publica-

tions, the study with the most inclusive data

was preferentially selected.

Selection of studies

Screening was performed independently by

two reviewers (L. T. Wong and W. L. Tan);

any disagreement between the reviewers was

resolved by discussion. The initial electronic

search resulted in the identification of 2843

titles from the MEDLINE – Pubmed database

and 1111 titles from the Cochrane Central

2 | Clin. Oral. Impl. Res. 23(Suppl. 5), 2012/1–21 © 2011 John Wiley & Sons A/S

Tan et al Dimensional tissue changes post extraction


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Register of Controlled Trials (CENTRAL).

After careful independent screening of the

titles and elimination of duplicate titles by

both the examiners, a total of 238 titles were

considered for possible inclusion. Retrieval of

the 238 abstracts and further perusal led to

104 full-text articles being selected. From

these full-text articles, 19 were identified for

inclusion in the review.

Another article was deemed suitable from

the secondary electronic search, but no addi-

tional publications from the hand-search or

the bibliography search of the selected arti-

cles were identified for inclusion.

In total, 20 articles were identified for

eventual inclusion in this review (Fig. 1).

A j-score of 0.84 was obtained, for consen-

sus between the two reviewers.

Exclusion of studies

Of the 104 full-text articles examined, 85

were excluded from the final analysis

(Table 1). The main reasons for exclusion

were that there were no actual measure-

ments of the dimensional changes of the

alveolar ridge, the reported parameters were

not useful for this review and that there was

the presence of a foreign material in the

extraction site during the healing phase,

among other reasons.

Data collection

From the selected papers that met the crite-

ria, data addressing dimensional changes

Potentially relevant

publications identified from

electronic search of

Cochrane Central Register of

Controlled Trials (CENTRAL)

database from 1st

January

1960 to 30th

June 2010

(n = 1111)

Potentially relevant

publications identified from

electronic search of

MEDLINE-Pubmed database

from 1st

January 1960 to 30th

June 2010

(n = 2843)

Publications excluded on the basis of title

and summary evaluation; also excluded

duplicate publications(n = 3716)

Potentially relevant full texts

retrieved for detailed

evaluation

(n = 104)

Publications excluded on the basis of full

text evaluation

(n = 85)

Studies included based on

the initial electronic search of

the MEDLINE-Pubmed and

CENTRAL database from 1st

January 1969 to 30th

June

2010

(n = 19)

Publications included based on the hand-

search and bibliography search of

relevant articles

(n = 0)

Publications included based on the

secondary electronic search of the

MEDLINE-Pubmed and CENTRAL

database from 1st

July 2010 to 31st

January 2011

(n = 1)

Studies included in the

present systematic review

(n = 20)

Fig. 1. Search strategy. Post-extraction dimensional changes.

Table 1. Studies failing to meet inclusion criteria

Reference Rationale for exclusion

Richardson 1965; Guglielmotti & Cabrini 1985; Guglielmotti et al. 1985; Mathai et al. 1989;

Ubios et al. 1991; Boyne 1995; Gauthier et al. 1999; Teofilo et al. 2001; Brandao et al. 2002;

Indovina & Block 2002; Magro-Ernica et al. 2003; Altundal & Guvener 2004; Bianchi et al. 2004;

Gorustovich et al. 2004; Nevins et al. 2006; Ortega et al. 2007; Araujo et al. 2008; Iino et al. 2008;

Agbaje et al. 2009; Puia et al. 2009; Alissa et al. 2010; Normando et al. 2010

Reported parameters not relevant or not useful

Pietrokovski & Massler 1967a; Matsumoto 1968 Length of observation period not reported

Amemori 1966; Mizutani & Ishihata 1976; Olson & Hagen 1982; Hahn et al. 1988; Oltramari et al.

2007; Shi et al. 2007; Fickl et al. 2008a; Fickl et al. 2008b

Studies carried out on animals

Loo 1968; Ashman & Bruins 1985; Ashman & Bruins1987; Scheer & Boyne 1987; Sclar 1999;

Minsk 2005

Descriptive report on procedure/ technique;

commentary

Guglielmotti et al. 1986; Hsieh et al. 1995; Fickl et al. 2008c; Rothamel et al. 2008; Araujo &

Lindhe 2009a; Pessoa et al. 2009

No baseline data available for comparison, thus unable

to arrive at an estimate of dimensional change overtime

Carlsson & Persson 1967; Pietrokovski & Massler 1967b; Pietrokovski 1967; Green et al. 1969;

Huebsch & Hansen 1969; Berkovitz 1971; Pietrokovski & Massler 1971; Hars & Massler 1972;

Librus et al. 1973; Thilander & Astrand 1973; Horn et al. 1979; Olson et al. 1982; Quinn &

Kent 1984; Lavelle 1985; Boyes-Varley et al. 1988; Magro-Filho & de Carvalho 1990; Dayan

et al. 1992; Alves-Rezende & Okamoto 1997; Anitua 1999; Pinto et al. 2002; Carmagnola

et al. 2003; Cardaropoli et al. 2005; Smith 1974; Ahn & Shin 2008; Serino et al. 2008; Sharan &

Madjar 2008; Luvizuto et al. 2010; Teofilo et al. 2010

No measurements of alveolar dimensional changes (e.g.

description of healing process or bony shape change,

or histology only)

Bergstedt et al. 1973; Michael & Barsoum 1976; Kangvonkit et al. 1986; Sattayasanskul et al.

1988

Study subjects had immediate dentures after extraction,

hence they did not have undisturbed healing

post-extraction

Bahat et al. 1987; Iizuka et al. 1992; Yugoshi et al. 2002; Araujo et al. 2005; Lindeboom et al.

2006; Wu et al. 2008; Araujo & Lindhe 2009b; Nevins et al. 2009

Sample did not include untreated/undisturbed extraction

sockets left to heal spontaneously

Araujo & Lindhe 2005 Only measured relative difference in height between

buccal and lingual plates of the alveolus

© 2011 John Wiley & Sons A/S 3 | Clin. Oral. Impl. Res. 23(Suppl. 5), 2012/1–21



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of both soft and hard tissues of the alveolar

ridge were retrieved for analysis. Mean

values and standard deviations, where

available, were extracted in duplicate by

the two reviewers (L. T. Wong and W. L.

Tan).

Quality assessment

Assessment of study quality was performedfor all the included papers. The Cochrane

Collaboration’s tool for assessing risk of bias

was used in the case of randomized con-

trolled clinical trials and controlled clinical

trials. Methodological quality assessment of

cohort studies was based on the Newcastle –

Ottawa Quality Assessment Scale for Cohort

studies (Tables 2 and 3).

Data synthesis

Preliminary evaluation of the selected publi-

cations revealed that there was considerable

heterogeneity between the studies withregard to study design, study population,

study period, method of assessment of

dimensional change of the alveolar ridge as

well as reference point from which the

changes were measured. Taking this into

consideration, it was not appropriate to con-

duct a quantitative data synthesis for all

studies, leading to a meta-analysis. In this

case, we attempted to report the data by

applying descriptive methods. In addition,

as a selected few of the included studies

demonstrated some similarity in measure-

ment methods and reference points, we pre-sented weighted means of the dimensional

change of the alveolar ridge over time as

appropriate, taking into account the values

of the relevant standard deviation and

applying inverse variance weighting (Meier

1953).

Inverse variance weighting

For the weighted mean of the list of data for

which each mean x i comes from a different

probability distribution with a known

variance r i2, the weight for each study is

given by:

W i ¼ 1

ri 2

The weighted mean in this case is:

x ¼

Pni ¼1ðxi =r

2

i ÞPni ¼1ð1=r

2i Þ

and the variance of the weighted mean is:

r2

x ¼ 1

Pni ¼1ð1=r

2i Þ

Assessment of heterogeneity

Statistical heterogeneity between all the

included studies was not assessed because all

the studies had different observation time

points as well as measurement methods,

making a statistical comparison impossible.

However, assessment of heterogeneity

between studies with similar characteristics

were performed using Cochran’s Q-test:

Q ¼X

wi ðxi xÞ

The P-value was then calculated for the Q

statistic and a value of P < 0.05 would indi-

cate significant statistical heterogeneity

between the studies.

When Q > df, where df is its degree of free-

dom, the I 2 index was also calculated using

the following formula:

I 2

¼

Q df

Q

100%

where, I 2 = 0% to 40% would indicate

there is little to no heterogeneity

I 2 = 30% to 60% would indicate there is

moderate heterogeneity

I 2 = 50% to 90% would indicate there is

substantial heterogeneity

I 2 = 75% to 100% would indicate consider-

able heterogeneity

Similarly, the P-value was calculated for

the I 2 statistic, and a value of P < 0.05 would

indicate a result that is statistically signifi-

cant.

Results

Collectively, a total of 20 studies satisfied

the inclusion criteria and were included in

this systematic review.

The 20 studies included 11 randomized

controlled clinical trials, five controlled clini-

cal trials and four cohort studies (Tables 2

and 3). The majority of studies did not state

the reasons for tooth extraction, but in the

studies that did, they included fractures, car-

ies, trauma, endodontic, prosthodontic,

orthodontic and periodontal reasons. Thirteen

papers only studied non-molar extraction

sites (Carlsson & Persson 1967; Lekovic et al.

1997, 1998; Yilmaz et al. 1998; Camargo

et al. 2000; Iasella et al. 2003; Serino et al.

2003; Fiorellini et al. 2005; Saldanha et al.

2006; Rodd et al. 2007; Barone et al. 2008;

Aimetti et al. 2009; Pelegrine et al. 2010),

while six studies (Bragger et al. 1994; Schropp

et al. 2003; Kerr et al. 2008; Crespi et al.

2009; Moya-Villaescusa & Sanchez-Pérez

2010; Rasperini et al. 2010) reported on data

including molar extraction sites and one

study (Oghli & Steveling 2010) did not spec-

ify where the extractions were performed.

Most of the data extracted concerned teeth in

control groups of studies that evaluated vari-

ous ridge preservation procedures (Lekovic

et al. 1997, 1998; Yilmaz et al. 1998; Camar-

go et al. 2000; Iasella et al. 2003; Serino et al.

2003; Fiorellini et al. 2005; Barone et al.

2008; Aimetti et al. 2009; Crespi et al. 2009;

Oghli & Steveling 2010; Pelegrine et al. 2010;

Rasperini et al. 2010), but other studies were

either designed specifically to evaluate post-

extraction alveolar changes (Carlsson & Pers-

son 1967; Schropp et al. 2003; Rodd et al.

2007; Moya-Villaescusa & Sanchez-Perez

2010) or the effect of smoking (Saldanha

et al. 2006) or ultrasound treatment (Kerr

et al. 2008) on these changes. In addition,

one included study (Bragger et al. 1994) was

actually designed to test the effect of

chlorhexidine mouthrinse on post-extraction

healing. Each paper that was included in

this review contributed a number of extrac-

tion sites, ranging from three to over a

hundred sites. The age range of the patients

in these studies was between 10.8 and

53.3 years.

Included studies

There were a total of 20 studies addressing

the hard and soft tissue dimensional changes

of the alveolar ridge in humans, with sponta-

neous undisturbed healing. The studies were

grouped according to the reported changes in

hard tissue, soft tissue, or a combination of

both hard and soft tissue.

Hard tissue changes

Vertical and horizontal linear hard tissue

changes in humans were reported indepen-

dently or in combination by 17 studies

(Tables 4 and 7).

Vertical linear hard tissue alteration

All 17 studies that reported on post-extrac-

tion hard tissue changes looked into the ver-

tical linear dimensional change of the

alveolus. Eight studies (Lekovic et al. 1997,

1998; Camargo et al. 2000; Iasella et al. 2003;

Serino et al. 2003; Barone et al. 2008; Aimetti

et al. 2009; Pelegrine et al. 2010) utilized

re-entry procedures with stents or titanium

pins as reference points (Fig. 2), one other

study (Rasperini et al. 2010) did not carry out

a re-entry procedure but nevertheless utilized

a stent for reference. An additional eight

studies (Carlsson & Persson 1967; Bragger

et al. 1994; Schropp et al. 2003; Fiorellini

et al. 2005; Saldanha et al. 2006; Kerr et al




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Table 2. Cochrane Collaboration’s tool for assessing risk of bias

Study design

Carlsson & Persson (1967) Brägger et al. (1994)

Controlled clinical trial Randomized controlled clinical trial

Parallel Parallel

Adequate sequence generation No Unclear

Remark Quote “alternate patients were assigned to respective

groups”

Quote “then randomly assigned”

Insufficient information about sequence generation

Allocation concealment Unclear Unclear

Remark No information provided. No information provided.Blinding Unclear Yes

Remark Study did not address this outcome. Quote “ double-blind clinical trial”

Incomplete outcome data addressed Yes No

Remark Quote “one patient from each group had to be

discarded….one had moved…other case first radiograph

unsuccessful and could not be repeated..”

Initially mentioned that 40 patients were enrolled in

study, but subsequently only obtained radiographs for

23 patients with no explanation

Free of selective reporting Yes No

Remark Initially mentioned that 40 patients were enrolled in

study, but subsequently only obtained radiographs for

23 patients with no explanation

Free of other sources of bias Yes Yes

Remark

Overall risk of bias High High

Study design

Lekovic et al. (1997) Lekovic et al. (1998)


Split-mouth Split-mouth

Adequate sequence generation Unclear Yes

Remark No information provided Quote “ control and experimental sites were assigned by

the flip of a coin”


Remark No information provided No information provided

Blinding Unclear Yes

Remark Study did not address this outcome Quote “clinical measurements were performed by one

clinician who did not have knowledge of control and

experimental sites”

Incomplete outcome data addressed Yes Yes

Remark Mentioned that three patient had dehiscence in test

group, hence did not measure values at 6 months;

re-entry was planned at 6 months, but if membrane

exposure occurred, re-entry and measurements was

done at 3 months. Refer to Tables 3 – 5 and will see that

they analysed the results with various combinations,including with or without the patients that exited early,

suggesting an intention-to-treat analysis

No missing outcome data

Free of selective reporting Yes Yes

Remark


Remark

Overall risk of bias Unclear Unclear

Study design

Camargo et al. (2000) Iasella et al. (2003) Serino et al. (2003) Fiorellini et al. (2005)

Controlled clinical trial

Randomized controlled

clinical trial Controlled clinical trial

Randomized controlled clinical

trial

Split-mouth Parallel Parallel and split-mouth Parallel

Adequate sequence

generation

Unclear Yes Unclear Unclear

Remark No information provided Quote “randomly selected

using a coin toss”

No information provided Quote “ cohorts of 40 patient

randomized in a double-blind

manner”

Insufficient information about

sequence generation

Allocation

concealment

Unclear Unclear Unclear Unclear

Remark No infor ma tion provided No informat ion provide d No inf ormat ion provided No inf or mation pr ovided

Blinding Unclear Yes Unclear Yes

Remark Study did not address this

outcome

Quote “measurements were

taken by 2 masked

examiners”

No information provided Quote “all the patients in the study

underwent the same surgical

procedure, regardless of the

treatment

Incomplete outcome

data addressed

Yes Yes Yes Yes




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Table 2. (continued)

Study design

Camargo et al. (2000) Iasella et al. (2003) Serino et al. (2003) Fiorellini et al. (2005)

Controlled clinical trial

Randomized controlled

clinical trial Controlled clinical trial


trial

Split-mouth Parallel Parallel and split-mouth Parallel

Remark No missing outcome data Quote “implants were

successfully placed at all

sites….none have been

subsequently lost”

Quote “nine subjects

dropped out from the

study for reasons unrelated

to the therapy”

Quote “ No subjects were

withdrawn or lost to follow-up”

Free of selectivereporting

Yes Yes Yes Yes

Remark

Free of other sources

of bias

Yes Yes Yes Yes

Remark

Overall risk of bias Unclear Unclear Unclear Unclear

Study design

Barone et al. (2008) Kerr et al. (2008) Aimetti et al. (2009)

Randomized controlled clinical trial Randomized controlled clinical trial


trial

Parallel Split-mouth Parallel

Adequate sequence generation Yes Unclear Unclear

Remark Quote “using a

computer-generated

randomisation list…”

Quote “ one site was assigned

randomly as test, whereas the

other site was assigned as control”

Quote “ were consecutively

selected..” and “ all sockets were

measured and assigned randomly

to test or control”Insufficient information about

sequence generation


sequence generation

Allocation concealment Unclear Unclear No

Remark No information provided No information provided Assignment not explicitly

concealed

Blinding Yes Yes Yes

Remark Quote “all measurements were

taken by one examiner who was

not involved in performing the

surgical treatment…”

Quote “examiner was masked as to

whether sites were test or control”

Quote “recorded by the same

examiner, who was not involved

in providing therapy”

Incomplete outcome data addressed Yes Yes Unclear

Remark No loss to follow-up in test and

control group

No missing outcome dat a St udy did not a ddr es s this

outcome

Free of selective reporting Yes Yes Yes

Remark

Free of other sources of bias Yes Yes Yes

RemarkOverall risk of bias Unclear Unclear High

Study design

Crespi et al. (2009) Pelegrine et al. (2010) Rasperini et al. (2010)



trial

Split-mouth Parallel Parallel

Adequate sequence generation No Unclear Yes

Remark Quote “sockets on right side of jaw

received MHA….sockets on left

side received CS…”

Quote “teeth to be extracted were

randomized into two groups”

Quote “treatment regimens were

assigned randomly to the subjects

with a balanced random permuted

block approach”

Allocation by left or right side

of jaw


sequence generation

Allocation concealment Unclear Unclear Yes

Remark No information provided. No information provided. Quote “treatment regimens

assigned randomly…

communicated to the operator

immediately after tooth

extraction”

Blinding Yes Unclear Yes

Remark Quote “a masked examiner

measured the bone level changes.”

Study did not address this outcome Quote “tubes included into the

stent by a blind examiner…..after

surgery, blinded examiner

positioned the stent.”

Incomplete outcome data addressed Yes Unclear Yes

Remark No missing outcome data Study did not address this outcome. Missing outcome data balanced in

numbers across groups

Free of selective reporting Yes Yes Yes

Remark

Free of other sources of bias Yes Yes Yes

Remark

Overall risk of bias High Unclear Low




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2008; Crespi et al. 2009; Moya-Villaescusa &

Sanchez-Pérez 2010) utilized imaging meth-

ods to obtain the required information.

Only one re-entry study (Aimetti et al.2009) addressed the vertical linear change of

the alveolar hard tissue post-extraction at

3 months. In this study, 3 months after

extraction of anterior maxillary teeth, a mean

vertical reduction of 1.2 ± 0.8 mm on the

buccal, 0.9 ± 1.1 mm on the palatal and

0.5 ± 0.9 mm on the mesial and distal sites

were reported when an acrylic stent was used

as a fixed reference during re-entry.

A total of six re-entry studies (Lekovic et al.

1997, 1998; Camargo et al. 2000; Iasella et al.

2003; Serino et al. 2003; Pelegrine et al. 2010)

reported data on 6-month post-extraction ver-tical linear hard tissue changes of the alveolus;

four studies (Lekovic et al. 1997, 1998; Camar-

go et al. 2000; Pelegrine et al. 2010) utilized a

titanium screw or pin, while two studies (Ia-

sella et al. 2003 and Serino et al. 2003) used an

acrylic stent as a fixed reference point.

Six months following the extraction of

anterior teeth or premolars, Lekovic et al.

(1997) reported a mean reduction of

1.2 ± 0.13 mm in buccal vertical ridge height,

while Lekovic et al. (1998) and Camargo

et al. (2000) reported a mean reduction of

1.50 ± 0.26 mm and 1.00 ± 2.25 mm respec-tively. Later, Pelegrine et al. (2010) showed

that 6 months after extraction of maxillary

anterior teeth, the mean buccal vertical alve-

olar ridge height reduction was

1.17 ± 0.26 mm. All the four studies men-

tioned above measure changes relative to a

titanium pin or screw at re-entry.

Iasella et al. (2003) and Serino et al. (2003)

utilized re-entry procedures and acrylic stents

as fixed references, 6 months after extraction

of non-molar teeth. The former study reported

an average alveolar vertical hard tissue reduc-

tion of 0.9 ± 1.6 mm at the mid-buccal,

0.4 ± 1.0 mm at the mid-lingual, 1.0 ± 0.8

mm at the mesial and 0.8 ± 0.8 mm on the

distal sites; the latter study recorded a meanreduction of 0.7 ± 1.2 mm on the buccal.

Taking into consideration the similarities

between these six re-entry studies that

reported 6-month data (Lekovic et al. 1997,


Serino et al. 2003; Pelegrine et al. 2010), the

weighted mean was calculated for the rele-

vant sites, using the inverse variance

method, to give a more robust value of the

6-month post-extraction vertical change

(Fig. 3). On the buccal, all six studies were

included to give a weighted mean reduction

of 1.24 ± 0.11 mm (Q = 1.3, P = 0.94). Onlytwo studies (Iasella et al. 2003; Serino et al.

2003) were included when mesial and distal

sites were investigated; the respective

weighted reductions were 0.84 ± 0.62 mm on

the mesial (Q = 0.10, P = 0.75) and

0.80 ± 0.71 mm on the distal (Q = 0, P = 1).

After a 7-month undisturbed healing period

in non-molar extraction sites, Barone et al.

(2008) observed vertical linear reduction of

3.6 ± 1.5 mm, 3.0 ± 1.6 mm, 0.4 ± 1.2 mm

and 0.5 ± 1.0 mm on the mid-buccal, mid-lin-

gual, mesial and distal sites respectively, at re-

entry. A stent was used as a fixed reference.Rasperini et al. (2010) reported on 3- and 6-

month dimensional changes of the alveolar

ridge after extraction of maxillary molar

teeth, using a custom acrylic stent and a peri-

odontal probe or endodontic file to obtain the

measurements; measurements were made

from the surface of the bone to the external

surface of the stent. The observed reduction

in height of the buccal plate at 3 and

6 months were 2.2 and 5.7 mm respectively,

when the buccal plates were intact after

extraction. However, when the buccal plates

were lost at time of extraction, there was a

corresponding gain of buccal bone height of 1

and 0.6 mm at 3 and 6 months respectively.

Radiographic methods used for the relevantstudies were: lateral cephalometric radiogra-

phy in one study (Carlsson & Persson 1967),

cone beam computed tomography in two

studies (Fiorellini et al. 2005 and Kerr et al.

2008), linear tomography in one study (Salda-

nha et al. 2006), and intraoral peri-apical radi-

ography in four studies (Bragger et al. 1994;

Schropp et al. 2003; Crespi et al. 2009 and

Moya-Villaescusa & Sanchez-Pérez 2010).

Carlsson & Persson (1967) attempted to

use lateral cephalometric radiography to dem-

onstrate the longitudinal height change in

the mandibular alveolar ridge after extractionof at least five to six lower anterior teeth and

loading with conventional full dentures

2 months post-extraction. The study had

observation time points at 2, 4, 6, 12, 24 and

60 months. The reductions in alveolar height

were 2.0 mm at 2 months, 2.9 mm at

4 months, 3.4 mm at 6 months and 4.1 mm

at 12 month, compared to baseline. From this

study, we can see a trend where there is a

large reduction in alveolar bone height in the

first 2 months post-extraction, followed by a

continual gradual resorption thereafter. Take

note that we should interpret the valuesobtained in this study, with observation time

points greater than 2 months, with caution;

2 months after teeth extraction, full dentures

were inserted in the conventional group, and

we cannot with full confidence, state that

insertion and use of denture prostheses did

not have an impact on the resorptive pattern

and extent of the alveolar hard and soft tis-

sues in this case.

Two studies (Fiorellini et al. 2005; Kerr

et al. 2008) utilized computed tomography to

detect vertical height changes in the alveolar

Table 2. (continued)

Study design

Yilmaz et al. (1998) Oghli & Steveling (2010)


Parallel Parallel

Adequate sequence generation Unclear Unclear

Remark No information provided Quote “patients were divided randomly into three groups”

Insufficient information about sequence generation


Remark No information provided No information provided

Blinding Unclear UnclearRemark Study did not address this outcome Study did not address this outcome

Incomplete outcome data addressed Unclear Yes

Remark Study did not address this outcome All exclusions accounted for

Free of selective reporting Yes Yes

Remark


Remark

Overall risk of bias Unclear Unclear




8/21

hard tissue. Fiorellini et al. (2005) reported a

4-month mean height reduction of

1.17 ± 1.23 mm in patients after extraction

of maxillary non-molar teeth; of note is that

all the patients in this sample had a buccal

defect of 50% bone loss of the extraction

socket at baseline. In the study by Kerr et al.

(2008), following extraction of a permanent

tooth, the corresponding vertical resorption

of the alveolar ridge were 1.01 ± 0.39 mm on

the buccal, 0.62 ± 0.28 mm on the lingual at

1 month and 0.95 ± 0.39 on the buccal,

1.12 ± 0.28 on the lingual at 3 months.

Six months after extraction of upper ante-

rior teeth, Saldanha et al. (2006) observed a

vertical resorption of 1.5 mm in smokers and

1.0 mm in non-smokers when using linear

tomography.

Assessing interproximal bone height

change on intraoral periapical radiographs,

Bragger et al. (1994) demonstrated a vertical

reduction of 0.61 ± 0.67 mm, 0.67 ±

0.66 mm, 1.19 ± 1.50 mm and 0.93 ± 0.74

mm at 1, 2, 3 and 6 months respectively,

while Schropp et al. (2003) documented a

0.3 mm loss at 12 months. Crespi et al.

(2009) went on to show an overall 3-month

Table 3. Newcastle – Ottawa Quality Assessment Scale for Cohort Studies (max 9*)

Study design

Schropp et al. (2003) Saldanha et al. (2006)

Cohort Cohort

Selection

Representativeness of the exposed

cohort

Truly representative of the average implant

patient in the community

Representative of the average patient

requiring extraction in the community

Rating * *

Selection of non exposed cohort No description of the derivation of non-exposed

cohort

No description of the derivation of the non-exposed

cohort

RatingAscertainment of exposure Secure record (radiograph, study model, clinical

exam)

Secure record (radiograph, linear tomography, clinical

exam)

Rating * *

Demonstration that outcome of

interest was not present at

start of study

Yes Yes

Rating * *

Comparability

Comparability of cohorts on the

basis of the design or analysis

No mention of control of any confounding factors (e.g.

smoking, health)

Controlled for confounding factors (smoking, oral

hygiene, ethnicity, systemic health)

Rating **

Outcome

Assessment of outcome Records (radiograph, study models) Independent blind assessment

Rating * *

Was follow-up long enough for

outcomes to occur

Yes; 12 months follow up (early soft/hard tissue healing

usually 6 – 8 weeks)

Yes; 6 months (early hard tissue healing usually

6 – 8 weeks)

Rating * *

Adequacy of follow up of cohorts Description of those lost to follow-up No statem ent

Rating *

Overall 6* 7*

Study design

Rodd et al. (2007) Moya-Villaescusa & Sanchez-Pérez (2010)

Cohort Cohort

Selection

Representativeness of the exposed

cohort

Truly representative of the average young patient

with dental trauma in the community

Representative of the average patient requiring

extraction in the community

Rating * *

Selection of non exposed cohort No description of the derivation of non-exposed

cohort

No description of the derivation of non-exposed

cohort

Rating

Ascertainment of exposure Secure record (study model, photograph, clinical

exam)

Secure record (radiograph, clinical exam)

Rating * *Demonstration that outcome of interest

was not present at start of study

Yes Yes

Rating * *

Comparability

Comparability of cohorts on the basis

of the design or analysis

Sample size too small to allow statistical

adjustment of confounders

Controlled for confounding factors (smoking, number

of roots, oral hygiene, periodontal disease)

Rating **

Outcome

Assessment of outcome Records (study model, photograph) Records (radiograph)

Rating * *

Was follow-up long enough for

outcomes to occur

Yes; 4 – 61 months follow up (early soft/hard tissue

healing usually 6 – 8 weeks)

Yes; 3 months follow up (early hard tissue healing

usually 6 – 8 weeks)

Rating * *

Adequacy of follow up of cohorts No statement No statement

Rating

Overall 5* 7*




9/21

loss of 3.75 ± 0.63 mm when the buccal plate

was lost during extraction. One study (Moya-

Villaescusa & Sanchez-Pérez 2010) further

discerned between the bone loss at 3 months

after extraction of single-rooted teeth

(4.16 ± 0.32 mm) vs. multiple-rooted teeth

(4.48 ± 0.39 mm loss), although the differ-

ence was not statistically significant. The

average bone loss when both groups were

combined was 4.32 ± 0.24 mm.

Percentage change of vertical linear hard tissuealteration

All the four re-entry studies (Lekovic et al.

1997, 1998; Camargo et al. 2000; Pelegrine

et al. 2010) utilizing a titanium pin or screw

had data on the baseline internal socket

height. This facilitated a calculation of the

percentage reduction of the vertical dimen-

sion of the alveolus post-extraction as fol-

lows:

%vertical linear change ðhard tissueÞ

¼ vertical linear resortion ðhard tissueÞbaseline internal socket height

The calculated percentage vertical change

of the alveolar hard tissue ranged from 11%

to 22% (Fig. 4) at buccal sites, 6 months

post-extraction.

Horizontal linear hard tissue alteration

A total of eight studies (Lekovic et al. 1997,


Barone et al. 2008; Kerr et al. 2008; Aimetti

et al. 2009; Pelegrine et al. 2010) reported on

horizontal changes over time in the hard tis-

sue at the level of the alveolar crest (Fig. 5).

Two studies (Kerr et al. 2008; Aimetti et al.

2009) reported 3-month horizontal reduction

to be between 2.20 and 3.20 mm; another

study (Barone et al. 2008) reported 7-month

reduction to be 4.5 ± 0.8 mm. Lekovic et al.

(1997, 1998), Camargo et al. (2000), Iasella

et al. (2003) and Pelegrine et al. (2010) docu-

mented 6-month horizontal reduction in the

hard tissue of the alveolar ridge to be 4.40,

4.56, 3.06, 2.63 and 2.46 mm respectively

The five latter studies (Lekovic et al. 1997,

1998; Camargo et al. 2000; Iasella et al. 2003

and Pelegrine et al. 2010) have quite a few

methodological similarities, however, results

of the heterogeneity testing reveal that there

is considerable heterogeneity between the

Table 4. Characteristics of studies included for hard tissue change only

Title

Author,

publishing year Species QA Tissue Methods

Sample

size

No. of

extraction

sites

Morphologic changes of the mandible after extraction

and wearing of denture

Carlsson 1967 human CCT Hard Radio 17 5 – 6 per pt

Effect of chlorhexidine(0.12%) rinses on periodontal

tissue healing after tooth extraction(II)radiographic

parameters

Bragger 1994 Human RCCT Hard Radio 12 21

A bone regeneration approach to alveolar ridgemaintenance following tooth extraction. Report of

10 cases

Lekovic 1997 Human CCT Hard Re-entry (pin) 10 10

Preservation of alveolar bone in extraction sockets

using bioabsorbable membranes

Lekovic 1998 Human RCCT Hard Re-entry

(pin 2 – 5 mm)

16 16

Influence of bioactive glass on changes in alveolar

process dimensions after exodontia

Camargo 2000 Human CCT Hard Re-entry

(pin 1 – 8 mm)

16 16

Ridge preservation with freeze-dried bone allograft

and a collagen membrane compared to extraction

alone for implant site development: a clinical and

histological study in humans

Iasella 2003 Human RCCT Soft

+ hard

Re-entry

(stent)

12 12

Ridge preservation following tooth extraction using

a polylactide and polyglycolide sponge as space filler:

a clinical and histological study in humans

Serino 2003 Human CCT Hard Re-entry

(stent)

12 13

Bone healing and soft tissue contour changes

following single-tooth extraction: a clinical and

radiographic 12-month prospective study

Schropp 2003 Human Cohort Hard Radio 46 46

Randomized study evaluating recombinant human

bone morphogenetic protein-2 for extraction socket

augmentation

Fiorellini 2005 Human RCCT Hard CT scan 20 ?

Smoking may affect the alveolar process dimensions

and radiographic bone density in maxillary extraction

sites: a prospective study in humans

Saldanha 2006 Human Cohort Hard Radio 21 21

Xenograft vs. extraction alone for ridge preservation

after tooth removal: a clinical and histomorphometric

study

Barone 2008 Human RCCT Hard Re-entry

(stent)

20 20

The effect of ultrasound on bone dimension changes

following extraction: a pilot study

Kerr 2008 Human RCCT Hard CBVT (ref

plate)

12 12

Clinical and histological healing of human extraction

sockets filled with calcium sulphate

Aimettl 2009 Human RCCT Hard Re-entry

(stent)

18 18

Magnesium-enriched hydroxyapatite compared to

calcium sulphate in the healing of human extraction

sockets: radiographic and histomorphometric

evaluation at 3 months

Crespi 2009 Human RCCT Hard Radio 15 15

Measurement of ridge alterations following tooth

removal:a radiographic study in humans

Moya-Villaescusa

2010

Human Cohort Hard Radio 100 100

Clinical and histomorphometric evaluation of

extraction sockets treated with an autologous bone

marrow graft

Pelegrine 2010 Human RCCT Hard Re-entry (pin) 6 15

Socket grafting in the posterior maxilla reduces the

need for sinus augmentation

Rasperini 2010 Human RCCT Hard Stent 3 3




10/21

studies (Q = 17.8, P < 0.05; I 2 = 77.6%,

P < 0.05). In this case, although the weighted

mean was calculated by applying the inverse

variance method to arrive at a value of

3.79 ± 0.23 mm horizontal reduction at

6 months (Fig. 6) across all five studies, the

robustness and applicability of this value

should be questioned.

Saldanha et al. (2006) reported the horizon-

tal reduction of the alveolar bone at 0% and

50% the distance from the crest. This study

demonstrated a 6-month reduction of 0.6 and

1.3 mm for non-smokers and smokers respec-

tively at 0% from the alveolar crest and cor-

responding values of 0.1 and 0.8 mm at 50%

from the crest. This study utilized linear

tomography to track the changes.

Of note, Kerr et al. (2008) demonstrated

beautifully that 3 months after tooth extrac-

tion, there was a relative decrease in horizon-

tal ridge reduction as the distance from the

alveolar crest increased (Fig. 7).

Percentage change of horizontal linear hard tissuealteration

All but one study (Kerr et al. 2008) reporting

changes in the ridge width also reported the

baseline ridge width immediately post-extrac-

tion. This facilitated a calculation of the per-

centage reduction of the horizontal dimension

of the alveolus post-extraction as follows:

%horizontallinear changeðhard tissueÞ

¼horizontal linear resortionðhard tissueÞ

baseline internal socket height

The calculated percentage horizontal

change of the alveolar hard tissue at the alve-

olar crest ranged from 32% at 3 months, and

between 29% and 63% after 6 – 7 months

post-extraction (Fig. 8).

Overall hard tissue changes

In general, with regard to vertical dimen-

sional change, we can see a trend where

there is a greater reduction on the buccal and

lingual sites as compared to the mesial anddistal sites. Looking at the horizontal dimen-

sional change, there is a distinct pattern of

resorption where the resorption decreases

with increased distance from the alveolar

crest. Overall, the observed horizontal resorp-

tion of the hard tissues (29 – 63%) is far

greater than the resorption in the vertical

dimension (11 – 22%), over an observation per-

iod of 3 – 7 months. It can be seen that the

bulk of the resorption occurs in the first

3 months post-extraction, and the changes

are much more subtle thereafter.

Fig. 2. Vertical (linear) hard tissue change for re-entry

studies only.

Fig. 3. Vertical (linear) hard tissue change for re-entry

studies only; weighted means shown.

Fig. 4. Vertical (linear) hard tissue percentage change in

four studies.

Fig. 5. Horizontal (linear) hard tissue change for re-

entry studies only.

Fig. 6. Horizontal (linear) hard tissue change for re-

entry studies only; weighted means shown.




11/21

Soft tissue changes

Only a single study (Iasella et al. 2003)

reported on longitudinal changes of soft tis-

sue dimensions in the alveolus post-extrac-

tion (Tables 5 and 7). This study

demonstrated a 0.4 – 0.5 mm gain of soft tis-

sue thickness at 6 months, measured at buc-

cal and lingual sites 3 mm from the alveolar

crest. Occlusally, soft tissue with thickness

of 2.1 mm developed after 6 months to com-

plete soft tissue coverage of the wound

(Fig. 9).

Combined hard and soft tissue changes

To date, a total of five studies (Carlsson &

Persson 1967; Yilmaz et al. 1998; Schropp

et al. 2003; Rodd et al. 2007; Oghli & Stevel-

ing 2010) presented data on the longitudinal

change in the combined hard and soft tissue

dimension of the alveolus post-extraction

(Tables 6 and 7). One study (Carlsson & Pers-

son 1967) utilized lateral cephalometric radi-

ography whereas study casts were employed

in the other four studies (Yilmaz et al. 1998;

Schropp et al. 2003; Rodd et al. 2007; Oghli

& Steveling 2010). Vertical and horizontal

linear tissue alterations were reported inde-

pendently or in combination; in one study

(Rodd et al. 2007) the overall areal change of

the alveolar hard and soft tissue combined,

was reported.

Vertical linear combined hard and soft tissuealteration

Three studies (Carlsson & Persson 1967; Yil-

maz et al. 1998 and Schropp et al. 2003)

addressed the combined hard and soft tissue

changes in the vertical dimension of the alve-

olus.

With the aid of lateral cephalometric radi-

ography, Carlsson & Persson (1967) was able

to demonstrate the combined hard and soft

tissue changes of the mandibular alveolus in

the vertical dimension over time. The verti-

cal reductions of the conjugated tissue

dimension from baseline were 2.1 mm at

2 months, 2.9 mm at 4 months, 3.4 mm at

6 months and 4.0 mm at 12 month. This

degree of resorption of the combined hard

and soft tissues followed a similar trend as

that of hard tissue alone.

Utilizing sectioned study casts, Yilmaz

et al. (1998) demonstrated a vertical reduc-

tion of 0.1 ± 0.52 mm and 0.5 ± 0.76 mm at

Fig. 7. Horizontal (linear) hard tissue change with

respect to distance from alveolar crest.

Fig. 8. Horizontal (linear) hard tissue percentage

change.

Table 5. Characteristic of study included for soft tissue change only

Title

Author,

Publishing Year Species QA Tissue Methods Sample size

No. of

extraction site

Ridge preservation with freeze-dried bone allograft

and a collagen membrane compared to extraction

alone for implant site development: a clinical and

histological study in humans

Iasella 2003 Human RCCT Soft + hard Re-entry (stent) 12 12

Table 6. Characteristics of studies included for both hard and soft tissue changes combined

Title Authors Species QA Tissue Method Sample size

No. of

extraction sites

Morphologic changes of the mandible after extraction

and wearing of denture

Carlsson 1967 Human CCT Soft + hard Radio 17 5/6 per pt

Alveolar ridge reconstruction and/or preservation

using root form bioglass cones

Yilmaz 1998 Human CCT Soft + hard Cast 5 10

Bone healing and soft tissue contour changes

following single-tooth extraction: A clinical and

radiographic 12-month prospective study

Schropp 2003 Human CCT Soft + hard Cast 46 46

Change in supporting tissue following loss of a

permanent maxillary incisor in children

Rodd 2007 Human Cohort Soft + hard Cast 16 16

Ridge preservation following tooth extraction:

A comparison between atraumatic extraction and

socket seal surgery

Oghli 2010 Human RCCT Soft + hard Cast 72 101

Fig. 9. Change in soft tissue dimensions over time.




12/21

3 and 12 months respectively, post-extrac-

tion of maxillary incisor teeth (Fig. 10).

Schropp et al. (2003) took measurements

from study casts taken immediately after as

well as 3, 6 and 12 months after extraction

of maxillary posterior teeth. Taking the

occlusal surfaces of adjacent teeth as refer-

ence, a reduction of 0.1 mm at 3 months

was followed by a net gain of 0.1 mm at

6 months and 0.4 mm at 12 months of the

buccal sites. Lingual sites demonstrated a

loss of 0.8 – 0.9 mm between 3 and 6 months,

Table 7. Overall results from all studies

Author,

Publishing Year Species T issue Methods

Sample

size

No. of

extraction

sites

Vertical dimensional

change

Horizontal dimensional

change

Carlsson 1967 Human Hard Radio 17 5 – 6 per pt 2 month: 2.0(0.9) 2 month: 2.2(1.1)

4 month: 2.9(1.7) 12 month: 3.6(0.5)

6 month: 3.4(2.1) 60 month: 4.0(1.5)

12 month: 4.1(2.7)

24 month: 4.9(3.7)

60 month: 7.3(3.7)Bragger 1994 Human Hard Radio 12 21 1 month: 0.61(0.67)

2 month: 0.67(0.66)

3 month: 1.19(1.50)

6 month: 0.93(0.74)

Lekovic 1997 Human Hard Re-entry (pin) 10 10 6 month: 1.2(0.13) 6 month: 4.4(0.61)

Lekovic 1998 Human Hard Re-entry (pin2 –

5 mm)

16 16 6 month: 1.50(0.26) 6 month: 4.56(0.33)

Camargo 2000 Human H ard Re-entry (pin1 –

8 mm)

16 16 6 month: 1.00(2.25) 6 month: 3.06(2.41)

Iasella 2003 Human Soft+

hard

Re-entry (stent) 12 12 6 month: B 0.9(1.6) 6 month: 2.6(2.3)

L 0.4(1.0)

M 1.0(0.8)

D 0.8(0.8)

Iasella 2003 Human Soft Re-entry (stent) 12 12 6 month: B 0.4(0.6)

L 0.5(1.5)

(Soft tissue thickness change)

Serino 2003 Human Hard Re-entry (stent) 12 13 6 month: B 0.8(1.6)

M 0.6(1.0)

D 0.8(1.5)

Schropp 2003 Human Hard Radio 46 46 12 month: M 0.3

D 0.3

Schropp 2003 Human Soft+

hard

Cast 46 46 3 month: B 0.1 3 month: 3.8

L 0.8 6 month: 5.1

6 month: B 0.1 12 month: 6.1

L 0.9

12 month: B 0.4

L 0.8

Fiorellini 2005 Human Hard CT scan 20 ? 4 month: 1.17(1.23)

Saldanha 2006 Human Hard Radio 21 21 6 month: 1.0 to 1.5 6 month: 0.1 to 1.3

Barone 2008 Human Hard Re-entry (stent) 20 20 7 month: B 3.6(1.5) 7 month: 4.5(0.8)

L 3.0(1.6)

M 0.4(1.2)

D 0.5(1.0)Kerr 2008 Human Hard CBVT

(ref plate)

12 12 1 month:B 1.01(0 .39) 1 month: 0.16(0.96)

L 0.62(0.28) 0.62(0.24)

3 month:B 0.95(0.9) 0.26(0.17)

L 1.12(0.28) 0.10(0.10)

3 month: 2.20(0.81)

1.30(0.24)

0.59(0.17)

0.28(0.10)

Aimettl 2009 Human Hard Re-entry (stent) 18 18 3 month: B1.2(0.6)

L 0.9(1.1)

M 0.5(0.9)

D 0.5(1.1)

Crespi 2009 Human Hard Radio 15 15 3 month: 3.75(0.63)

Moya-Villaescusa

2010

Human Hard Radio 100 100 3 month: 4.32(0.23)

Pelegrine 2010 Human Hard Re-entry (pin) 6 15 6 month: 1.17(0.26)

Rasperini 2010 Human Hard Stent 3 3 3 month: 2.2

6 month: 5.7(4.2)

Yilmaz 1998 Human Hard Cast 5 10 3 month: 0.1(0.52) 3 month: 0.1(0.23)

12 month: 0.5(0.76) 12 month: 0.4(0.48)

Rodd 2007 Human Hard Cast 16 16 3 month: 15.7%

6 month: 25.3%

9 month: 22%

(Bone surface area)

Oghli 2010 Human Hard Cast 72 101 3 month: 0.3(0.5)




13/21

with a net loss of 0.8 mm at 12 months

(Fig. 10).

Horizontal linear combined hard and soft tissuealteration

Four studies (Carlsson & Persson 1967; Yil-

maz et al. 1998; Schropp et al. 2003; Oghli &

Steveling 2010) presented data on the com-

bined hard and soft tissue change in the hori-

zontal dimension following extraction.

The only study using radiographic methods

(Carlsson & Persson 1967) demonstrated a

reduction of the alveolar width in the magni-

tude of 2.2 mm at 2 months, which subse-

quently increased to 3.6 mm at 12 months;

this measurement was taken 3 mm from the

alveolar crest.

Study casts were used in some of the stud-

ies (Yilmaz et al. 1998; Schropp et al. 2003;

Oghli & Steveling 2010) to evaluate the

change in the horizontal dimension (Fig. 11).

Yilmaz et al. (1998) showed a 3- and 12-

month reduction in width of 0.1 ± 0.23 mm

and 0.4 ± 0.48 mm respectively, while Oghli

& Steveling (2010) reported a 3-month reduc-

tion of 0.3 ± 0.5 mm. Horizontal resorption

of the alveolar hard and soft tissue between 3

and 12 months was also reported by Schropp

et al. (2003); at 3 months the resorption was

3.8 mm, this increased to 5.1 mm at

6 months and culminated to a value of

6.1 mm at 12 months.

The latter three studies (Yilmaz et al.

1998; Schropp et al. 2003; Oghli & Steveling

2010) had quite many similarities and an

attempt to calculate the weighted means for

these three studies was launched. However,

the study by Schropp et al. (2003) failed to

provide any information on the standard

deviations in the study, so it was impossible

to utilize the inverse variance method to cal-

culate the weighted means.

Cross-sectional surface area alteration of combinedalveolar hard and soft tissues

A single study reported on change in alveolar

surface area of the hard and soft tissues com-

bined (Rodd et al. 2007); measurements were

obtained from study casts acquired prior to,

and at 3, 6 and 9 months following extrac-

tion of maxillary central incisors in children.

The reductions in surface area were presented

as a percentage of the surface area on the pre-

extraction cast, and were as follows: 15.7%

at 3 months, 25.3% at 6 months and 22% at

9 months.

Overall combined hard and soft tissue changes

With the aid of various assessment methods,

a longitudinal change of the combined hard

and soft tissues in the vertical dimension

was found to be anywhere between a loss of

4.0 mm to a gain of 0.4 mm over a period of

2 – 12 months.

Study casts and radiographs were employed

to assess the reduction of the combined hard

and soft tissues in the horizontal dimension.

This reduction was demonstrated to be

between 0.1 and 6.1 mm when the observa-

tion periods varied from 3 to 12 months, and

the measurements were taken at the alveolar

crest. When the measurements were taken

3 mm apical to the alveolar crest, the corre-

sponding horizontal reductions of the com-

bined hard and soft tissues were 2.2 mm at

2 months and 3.6 mm at 12 months. Reduc-

tions in cross-sectional surface area of the tis-

sues were up to 22% after 9 months.

Mimicking the changes of the alveolar hard

tissue, there is a similar pattern of resorption

when we look at the combined hard and

soft tissue entity; the horizontal alteration is

always more substantial than the vertical

change.

Discussion

The 20 included studies in this systematic

review were of different study designs and

measured dimensional change in variousways.

Eleven randomized controlled clinical tri-

als, five controlled clinical trials and four

cohort studies were included in this review.

It is common knowledge that randomized

controlled clinical trials and the systematic

review of randomized controlled clinical tri-

als provide the highest level of evidence

related to intervention and therapy. However,

in the case of post-extractional dimensional

changes of the alveolar hard and soft tissues,

there are no randomized controlled clinical

trials where the control procedure is wherethe tooth was left in situ and the test proce-

dure was extraction. Hence, the cohort stud-

ies where post-extraction alveolar hard and

soft tissues changes were monitored longitu-

dinally might provide better insight and be

the more appropriate study design.

The three main measuring methods uti-

lized were: (i) re-entry (ii) imaging and (iii)

study models. The re-entry method consti-

tuted of elevating a flap during extraction

and again at re-evaluation. All the studies

using the re-entry method measured the

parameters from a fixed reference, namely anacrylic stent or a titanium pin or screw. The

imaging method included the utilization of

periapical radiographs, lateral cephalometric

radiography, or computer tomography. The

method where study models were utilized

required that study impressions be taken

before, or immediately after extraction, and

again at re-evaluation.

Re-entry studies evaluated hard tissue as

well as soft tissues as separate entities, while

imaging studies evaluated either hard tissue

dimension only, or the combined hard and

soft tissue changes. Study model studiesfocused on combined hard and soft tissue

dimensional changes. During data analysis

process, we subdivided the data into different

groups, mainly according to measurement

methods and the tissues involved. The

groups include (i) hard tissue group, (ii) soft

tissue group, and (iii) combined hard and soft

tissue group.

Heterogeneity assessment

The 20 included studies had different obser-

vation time points, methodologies, and

Fig. 10. Vertical (linear) change of hard and soft tissues

combined.

Fig. 11. Horizontal (linear) change of hard and soft tis-

sues combined.




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measurement methods. Heterogeneity assess-

ment was performed in six re-entry studies

(Lekovic et al. 1997, 1998; Camargo et al.

2000; Iasella et al. 2003; Serino et al. 2003

and Pelegrine et al. 2010) calculating mean

vertical hard tissue change, and five studies

(Lekovic et al. 1997, 1998; Camargo et al.

2000; Iasella et al. 2003 and Pelegrine et al.

2010,) calculating horizontal hard tissue

change. These studies had similarity in terms

of the method of measurements employed.

The studies all employed re-entry methods,

utilizing an acrylic stent or a titanium pin or

screw as a fixed reference from which to

measure the dimensional changes. The differ-

ences in sample sizes, different behaviours of

study populations, varied observation time

points and measurement parameters contrib-

uted to the heterogeneity. Although weighted

means were calculated, the resultant values

should really only be used for reference pur-

poses. The robustness and applicability of the

weighted means should be interpreted with

caution.

Hard tissue vertical dimensional change

Buccal/lingual vs. mesial/distal

Three studies (Iasella et al. 2003; Barone

et al. 2008; Aimetti et al. 2009) measured

vertical dimensional changes of all the buc-

cal, lingual, mesial and distal bone plates.

Two of the three studies, namely Barone

et al. (2008) and Aimetti et al. (2009), demon-

strated that buccal/lingual sites (0.9 – 3.6 mmloss at 3 – 7 months) had more resorption than

mesial/distal sites (0.4 – 0.5 mm loss at 3 –

7 months). Referring to the calculated values

of the respective weighted mean, buccal bone

plates (1.24 mm loss at 3 – 7 months) also had

a tendency to resorb more than mesial/distal

bone sites (0.8 – 0.84 mm at 3 – 7 months)

(Fig. 2). One possible explanation for this

trend is that the mesial and distal bone levels

are partially determined by the presence or

absence of neighbouring teeth; mesial/distal

bone levels are held stable by the presence of

adjacent teeth.

Buccal vs. lingual

Iasella et al. (2003), Barone et al. (2008) and

Aimetti et al. (2009) measured vertical

dimensional changes at both buccal and lin-

gual bone plates. All three studies showed

that the buccal plate resorption (0.9 – 3.6 mm

at 3 – 7 months) was of greater magnitude

than that of the lingual plate (0.4 – 3 mm at 3

– 7 months). This finding was similar to pre-

vious studies in the canine model (Araujo &

Lindhe 2005; Araujo et al. 2005). This pattern

of resorption can be explained by the bundle

bone concept as proposed by Araujo & Lind-

he (2005). According to this theory, a larger

proportion of the buccal plate is made up of

bundle bone relative to the lingual plate; as

bundle bone is a tooth-dependent tissue, it is

quickly resorbed after tooth extraction and

with its resorption, a substantial portion of

the buccal plate is lost. In our review of the

literature, however, the relative height differ-

ence between the buccal and lingual bone

plates in humans was less marked compared

to the canine model by Araujo & Lindhe

(2005). The relative difference in height of

the buccal and lingual plate is estimated to

be around 0.3 – 0.6 mm over a period of 3 and

7 months, in our review. One possible expla-

nation for the observed differences between

human models and canine models is that the

buccal plate in humans is on average equally

prone to resorption as the lingual aspect of

the ridge (Van der Weijden et al. 2009).

Mesial vs. distal

Four studies (Iasella et al. 2003; Serino et al.

2003; Barone et al. 2008 and Aimetti et al.

2009) measured vertical dimensional changes

of both mesial and distal bone plates. All four

studies showed the extent of resorption to be

between 0.4 and 0.8 mm over an observation

period of 3 – 7 months.

Hard tissue vertical dimensional percentagechange

Lekovic et al. (1997, 1998), Camargo et al.(2000), Pelegrine et al. (2010) reported base-

line data of the internal socket height imme-

diately post-extraction. Internal socket height

is a measurement from buccal bone crest to

the bottom of the extraction socket. The pro-

vision of baseline internal socket height

enabled us to calculate the percentage change

in height of the buccal bone wall relative to

the baseline height of the buccal bone wall

over time. The percentage change reflected

the amount of vertical resorption of the buc-

cal plate only; this was found to be between

11% and 22% six months post-extraction.Percentage changes of lingual, mesial and

distal bony plates could not be calculated due

to lack of baseline data, but it is expected to

be less than 11 – 22%, as the amount of

resorption in these areas have been shown to

be of a comparatively lesser magnitude. Cor-

respondingly, from this this percentage, we

can interpret that there might be 78 – 89%

bone fill of the original socket height, calcu-

lated as percentage vertical bone fill equals

one minus vertical dimensional percentage

change.

Hard tissue horizontal dimensional change

Five re-entry studies (Lekovic et al. 1997,


Pelegrine et al. 2010) showed that there was

range of 2.46 – 4.56 mm horizontal bone loss

and weighted mean resorption of 3.79 mm at

6 months. However, theses studies only pro-

vided data for horizontal resorption at the

level of the alveolar crest, no data was avail-able on magnitude of horizontal resorption a

distance away from the alveolar crest. Kerr

et al. (2008) demonstrated a relative decrease

in horizontal ridge reduction as the distance

from the alveolar crest increased. This find-

ing was similar to a dog study done by Ara-

ujo & Lindhe (2009), which observed more

resorption at coronal third and least resorp-

tion at apical third of the alveolar ridge.

Hence, it is expected that the amount of hor-

izontal resorption might be less than

weighted mean of 3.79 mm at 6 months

when the measurement is taken at a distancefrom the alveolar crest.

Hard tissue horizontal dimensional percentagechange

There was 32% reduction at 3 months, and

29 – 63% reduction in horizontal dimension

at 6 months. This demonstrated that possi-

bly more than half of the ridge width could

be resorbed after 6 months in some patients.

However, a definite conclusion cannot be

drawn from these data, on whether the

resorption was from the buccal or lingual.

Studies by Pietrokovski & Massler (1967),Schropp et al. (2003), Araujo & Lindhe

(2005) and Barone et al. (2008) all suggest

that tissue loss is more pronounced on the

buccal aspect than from the lingual or pala-

tal aspect.

Vertical hard tissue vs. horizontal hard tissuechange

The amount of horizontal dimensional

change was found to be greater than that of

the vertical dimension, in both absolute val-

ues and percentage change. Horizontal reduc-

tion (3.79 ± 0.23 mm) was more than vertical

reduction (1.24 ± 0.11 mm on buccal, 0.84 ±

0.62 mm on mesial and 0.80 ± 0.71 mm on

distal) at 6 months. Percentage vertical

change was 11 – 22% at 6 months while per-

centage horizontal change was 32% at

3 months, and 29 – 63% between 6 and

7 months.

Soft tissue changes

Only one study by Iasella et al. (2003) was

found to have measured soft tissue thickness

change after extraction. There was a 0.4 –




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0.5 mm gain in soft tissue thickness on buc-

cal and lingual sites at 6 months. Interest-

ingly, from this study, a difference was found

in the change of soft tissue thickness over a

natural healing socket, and sockets aug-

mented using bio-resorbable membranes and

grafts. There was net gain of soft tissue

thickness in the natural healing group and a

net loss in the augmented group. One possi-

ble explanation for this observation was that

the membrane or graft placed might have

interfered with the soft tissue vascularity in

the augmented group. We must remember

that the vascular supply to the soft tissue is

derived from the underlying bone, and the

placement of membranes or grafts might

interfere with re-vascularization of the soft

tissues. In contrast, there is no interposing

material between the bone and the overlying

soft tissues in the naturally healing sockets.

Although there was an observed gain in soft

tissue thickness over a naturally healing

socket, a robust conclusion cannot be drawn

from this single study.

In addition, this study also demonstrated a

trend where the lingual soft tissues were

thicker than that on the buccal; lingual soft

tissues were nearly twice as thick. The meth-

ods and materials in the study could explain

this difference; majority of teeth extracted

within the study were maxillary teeth where

palatal soft tissue is expected to be much

thicker than that of the buccal. Hence, this

finding may only be applicable to the maxil-

lary extraction sockets, but not mandibular

ones. Note that this study only had a sample

size of 12 non-molar extraction sockets,

hence we should be cautious when trying to

interpret the results of this study.

Vertical combined hard and soft tissue change

Two studies by Yilmaz et al. (1998) and Sch-

ropp et al. (2003) demonstrated very subtle

changes in the vertical dimension of the hard

and soft tissues combined, between 3 and

12 months post-extraction. The changes ran-

ged from a gain of 0.1 mm to a loss of

0.9 mm at 6 months and a gain of 0.4 mm to

a loss of 0.8 mm at 12 months. Schropp et al.

(2003) also observed a small increase buccally

and a reduction orally.

Horizontal combined hard and soft tissuechange

Three studies (Yilmaz et al. 1998; Schropp

et al. 2003 and Oghli & Steveling 2010)

reported data on horizontal hard and soft tis-

sue changes. The studies by Yilmaz et al.

(1998) and Schropp et al. (2003) had a follow-

up of up to 12 months; both studies exhib-

ited a trend where there was a rapid reduc-

tion in first 3 months and gradual change

from thereafter, up to 12 months. Weighted

mean reduction showed this change to be

1.3 mm at 3 months and 5.1 mm at

12 months.

Vertical vs. horizontal combined hard and softchange

Hard and soft tissue showed a combined hori-

zontal reduction of 0.1 – 3.8 mm and 5.1 mm

at 3 and 6 months respectively. Correspond-

ingly, in the vertical dimension, this change

was between 0.1 and 0.8 mm reduction at

3 months, and 0.1 mm gain to 0.9 mm

reduction at 6 months. Overall, the demon-

strated horizontal change was more substan-

tial than the vertical change.

Combined hard and soft tissue change vs. hardtissue change only

In the horizontal dimension, the combinedhard and soft tissue reduction was 5.1 mm at

6 months, while the corresponding hard

tissue reduction was between 2.46 and

4.56 mm, with a weighted mean reduction of

3.79 mm.

Hence, at 6 months post-extraction, the

combined hard and soft tissues demonstrated

a tendency towards a more substantial reduc-

tion than hard tissue only; this observation is

not corroborated in the vertical aspect.

In the vertical dimension, when consider-

ing only hard tissue change (loss of 0.4 –

1.5 mm at 6 months), the magnitude of thischange was greater than that of the hard and

soft tissues combined (0.1 mm gain to

0.9 mm reduction at 6 months). A plausible

explanation might be that the increase in soft

tissue thickness (gain of 2.1 mm occlusally

vs. gain of only 0.4 – 0.5 mm on buccal/lin-

gual) compensated for the reduction in hard

tissue height.

Possible factors affecting dimensional changeafter tooth extraction

Flap vs. flaplessUsing a canine model, Fickl et al. (2008a)

demonstrated that there was significant dif-

ference of the extent of bone resorption

between flap and flapless extractions. The

flapless group had lower extent of resorption

compared to the flap group. Blanco et al.

(2008) also showed similar trend in another

study, although the study was investigating

ridge alterations after immediate implants

with or without flap. However, Araujo &

Lindhe (2009) found that the differences

between the flap and flapless groups in their

study were negligible after 6 months. Hence,

raising a flap during extraction may only

affect the short-term dimensional alterations

of the alveolar ridge.

Overeruption of adjacent teeth

Mizutani & Ishihata (1976) found that the

over-eruption of teeth adjacent to the extrac-

tion socket affected the overall dimensionalchange of ridge. The vertical alveolar ridge

height in this study decreased slightly ini-

tially, followed by a gradual increase later on,

which negated the previous reduction or even

surpassed the amount of resorption to result

in a net gain. The study speculated that the

over-eruption of teeth adjacent to extraction

sites might have affected the pattern of

dimensional change observed.

Smoking

Smoking may affect the extent of vertical

reduction of the alveolar ridge after extrac-

tion. Saldanha et al. (2006) showed that

there was a significant difference in dimen-

sional reduction between smoking and non-

smoking groups. There was vertical alveolar

ridge reduction of 1.5 mm in smokers and

1.0 mm in non-smokers, 6 months post-

extraction.

Single-rooted vs. multiple-rooted teeth

Moya-Villaescusa & Sanchez-Pérez (2010

study showed there was no significant differ-

ence in vertical dimensional change between

single-rooted (4.16 mm loss) and multi-rooted

teeth (4.48 mm loss), although there was a

tendency that multi-rooted teeth exhibited

greater resorption of the alveolar ridge.

Chlorhexidine

Rinsing with 15 ml of 0.12% chlorhexidine

digluconate mouthrinse twice daily for

1 month, starting 2 days after extraction may

have some effect on the observed vertical

change of the mesial and distal bone. Bragger

et al. (1994) showed that patients rinsing for

1 month with a placebo solution lost almost

1 mm of bone height over a 6-month period

after extraction, while in patients rinsing

with the chlorhexidine solution, the crestal

alveolar bone level was maintained.

Immediate denture

Carlsson & Persson (1967) showed that there

was no significant difference in alveolar

dimensional change between patients with

immediate or conventional dentures in the

long-term. Take note, however, that the

usage of immediate dentures had a tendency

to affect dimensional change in short-term,



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A RS of Post-extractional Alveolar Hard and Soft Tissue Dimensional Changes